Hybrid protective relay having enhanced contact response time

Abstract

A protective relay of the type consisting of a relay contacts controlled by means of a relay coil further includes a pair of triacs controlled by an optical switch. The high speed response is attributed to the configuration of the triacs while high ampere rating is provided by the contacts.

I claim: 
     
       1. A protective relay, comprising: an electromagnetic coil arranged for separating a pair of contacts upon command, said contacts being connected across first and second output terminals;   a photoelectric switch arranged in parallel with said coil;   an electronic switch arranged in series with said coil for energizing said coil and separating said contacts; and   a series connection of a semiconductor switch and a semiconductor switch protection fuse, said series connection being arranged in parallel with said contacts and said semiconductor switch being gated by said photoelectric switch, whereby said semiconductor switch turns on prior to complete closure of said contacts;   wherein said semiconductor switch protection fuse connected in series with said semiconductor switch disconnects said semiconductor switch if said semiconductor switch becomes shorted.   
     
     
       2. The protective relay of claim 1 including a first resistor connecting between said photoelectric switch and said semiconductor switch. 
     
     
       3. The protective relay of claim 2 including a second resistor connecting between said semiconductor switch and said second output terminal. 
     
     
       4. The protective relay of claim 1 including a reverse diode connecting across said photoelectric switch to protect said switch from reverse voltage conditions. 
     
     
       5. The protective relay of claim 1 wherein said photoelectric switch includes a photodiode. 
     
     
       6. The protective relay of claim 1 wherein said photoelectric switch includes a first triac. 
     
     
       7. The protective relay of claim 1 wherein said electronic switch comprises a transistor. 
     
     
       8. The protective relay of claim 1 wherein said semiconductor switch comprises a second triac. 
     
     
       9. The protective relay of claim 1, wherein the first and second output terminals connect with a data communications bus of a data processing system. 
     
     
       10. A protective relay, comprising: an electromagnetic relay coil controlling a pair of contacts, said contacts being connected across a first output terminal and a second output terminal and said relay coil being adapted to receive a turn-on current signal;   a photoelectric switch connected in parallel with said relay coil, said photoelectric switch becoming turned on upon receipt of said turn-on current signal;   an electronic switch connected in series with said relay coil, said electronic switch being adapted for receiving a turn-on voltage signal for initiating said turn-on current signal to said relay coil; and   a series connection of a semiconductor switch and a semiconductor switch protection fuse, said series connection being connected in parallel with said contacts, said semiconductor switch becoming turned on with said photoelectric switch whereby said semiconductor switch becomes turned on before said contacts becomes closed to provide output signals to said first and second output terminal.   
     
     
       11. The protective relay of claim 10 wherein said electronic switch comprises a transistor, said transistor being connected in series with said relay coil and having a base adapted for receiving said turn-on voltage. 
     
     
       12. The protective relay of claim 10 wherein said photoelectric switch comprises a photo-diode and a first photo-responsive triac responsive to said photodiode. 
     
     
       13. The protective relay of claim 12 wherein said semiconductor switch comprises a second triac connected in parallel with said first photo-responsive triac and said contacts. 
     
     
       14. The protective relay of claim 13 including a fuse connected in series with said second triac and said second terminal to protect said photoelectric switch and said semiconductor switch from overcurrent and overvoltage conditions.